Host, build and target are set to x86_64-pc-linux-musl.
$ grep -n AS_FOR_TARGET support/cpp/configure.ac 94:m4_pattern_allow([^AS_FOR_TARGET$])dnl 3385:ACX_CHECK_INSTALLED_TARGET_TOOL(AS_FOR_TARGET, as) 3403:GCC_TARGET_TOOL(as, AS_FOR_TARGET, AS, [gas/as-new]) 3443:COMPILER_AS_FOR_TARGET='$(AS_FOR_TARGET)' 3449: COMPILER_AS_FOR_TARGET='$$r/$(HOST_SUBDIR)/gcc/as' 3456:AC_SUBST(COMPILER_AS_FOR_TARGET) Likely the problem comes from ACX_CHECK_INSTALLED_TARGET_TOOL and possibly the specific build configuration.
Setting DEFAULT_ASSEMBLER allowed the build to succeed.
SDCC 4.5.0: Build failure at support/cpp/gcc
LGTM.
LGTM.